Rectifying arrangement comprising photo-resistive alarm circuits to indicate rectifier failure



March 1966 P. H. G. VAN VLODROP 3,233,520

REGTIFYING ARRANGEMENT COMPRISING PHOTORESISTIVE ALARM CIRCUITS TO INDICATE RECTIFIER FAILURE Filed Jan. 4, 1962 2 Sheets-Sheet 1 PHO O- RESISTOR INVENTOR PETER HG.VAN VLODROP AGEN March 1, 1966 VAN VLQDROP 3,238,520

RECTIFYING ARRANGEMENT COMPRISING PHOTORESISTIVE ALARM CIRCUITS TO INDICATE RECTIFIER FAILURE Filed Jan. 4, 1962 2 Sheets-Sheet 2 ll H H H H I I"! I ii?! L: 2 lr- U U 0 o 5 Q Q Q R W H II II I I l 1 ILJI INVENTOR PETER H.G.VAN VLODROP BY M x. AGEN United States Patent 3,238,520 RECTIFYING ARRANGEMENT COMPRISING PHOTO-RESISTIVE ALARM CIRCUITS T0 INDICATE RECTIFIER FAILURE Peter Hnbertus Gerardus van Vlodrop, Emmasingel, Eir 'dhoven, Netherlands, assignor to North American PllIllpS Company, Inc., New York, N.Y., a corporation of Delaware Filed Jan. 4, 1962, Ser. No. 164,260 Claims priority, application Netherlands, Oct. 2, 1961, 259,823 8 Claims. (Cl. 340-253) This invention relates to rectifying circuits comprismg a plurality of semi-conductive rectifying elements and more particularly to circuits of this type which incorporate control and/ or safety means.

In rectifying arrangements comprising gas-filled tubes or vacuum tubes it is comparatively simple to control the operation of the various tubes in the individual phases. Vacuum tubes are usually not connected in series so that an indication of the current for each phase suflices for detecting a defective element therein. Gas-filled tubes, however, are connected in series, but because of the small number of tubes per series it is then relatively easy to find the defective tube by exchanging tubes in that phase in which the absence of light phenomena indicates the interruption of current.

However, in rectifying arrangements comprising semi- ,conduct-ive rectifying elements in which, as a rule, more than two elements are-connected in series and also in many cases two or more branches are connected in parallel for each phase, it is not as easy to detect a defective element. In the majority of cases a defect occurs in the form of a short-circuit or a decrease in blocking resistance of the semi-conductor element. As a result, an overload condition arises due to the excessive inverse voltage occurring across the semi-conductor elements connected in series with the defective semi-conductor ele- 'ment. If the arrangement is not switched ofi in time and the defective element replaced, the other elements may also be damaged.

According to the invention, in a rectifying arrangement comprising a plurality of semi-conductive rectifying elements which incorporates control and/or safety means, a glow-discharge lamp and a series-resistor are connected in parallel with each rectifying element, the lamp being ignited at the inverse voltage of the element. A photoresistance element is optically compled with each glowdischarge lamp and receives light only from the associated lamp. All of the photo-resistance elements are connected in series and included in a relay circuit coupled to alarm and/ or safety means.

When all of the rectifying elements operate satisfactorily, all of the photo-resistance elements are illuminated by the glow-discharge lamps and the total resistance i thereof is comparatively low. The voltage source for the relay circuit may then deliver a comparatively large current through the series-combination, which current is sufficient for holding the relay in the alarm or safety circuit. However, if one of the rectifying elements is short-circuited or the blocking resistance becomes unduly low, the associated glow-discharge lamp can no longer be ignited due to the absence of sufficient inverse voltage across said element. The resistance of the associated photo-resistance element then remains high so that only a small current can flow in the relay circuit and the relay is de-energized. As a result, an alarm is rung or the arrangement is switched off. If the arrangement is not switched off, the defective rectifying element may be found by observing which of the glow-discharge lamps do not flash on.

In a rectifying arrangement comprising a large number of elements, it is usually not necessary immediately to switch off the whole arrangement for a single defective element. In this case, actuating an alarm sufiices. However, if two or more elements become defective, especially if they are connected in series, the arrangement must, as a rule, be switched off immediately. According to the invention, this may be ensured in a particular embodiment in a simple manner by connecting a constant resistor in parallel with each photo-resistance element. With suitable proportioning, there is in this case sufficient difference in series-resistance between the case in which one photo-resistance element only is not illuminated and the case in which two or more such elements are not illustrated to provide a suitable indication thereof.

In order that the invention may be readily carried into effect, it will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIGURE 1 shows a rectifying arrangement according to the invention:

FIGURES 2 and 3 show the relative arrangement of the glow-discharge lamps and the photo-resistance elements.

FIGURE 1 shows a three-phase transformer T in which two parallel branches of three series-connected silicon diodes D each in series with a safety fuse F, are connected to each secondary phase. A neon lamp L and a series-resistor R are connected in parallel with each diode D A photo-resistance element W is optically coupled with each glow-discharge lamp L and a constant resistor R is arranged in parallel with each photoresistance element. All of the photo-resistance elements W are connected in series in a circuit, supplied from terminals K and K of an alternating-current supply line through a silicon diode D provided with a smoothing capacitor C Three resistors R R and R of highohmic values are connected in series with the photo-resistance elements W. The half-wave rectifier formed by the rectifier element D also supplies two relay control tubes B, and B of the grid controlled gas discharge type through current-limiting resistors R and R respectively, and through relays S and S respectively, bridged by capacitors C and C respectively. The igniting electrode of tube B is connected to the positive end of resistor R and the igniting electrode of tube B is connected to the positive end of resistor R Capacitors C and C are included with the tubes B and B in the igniting circuit to ensure sufiicient igniting current when the igniting voltage of the auxiliary anode is reached. In each of the tubes B and B a guard electrode is arranged behind the anode and connected through resistors R and R respectively, to the cathode.

The rectifier D delivers a pulsatory direct voltage which causes a flow of pulsatory direct current through the series-combination of the photo-resistance elements and the resistors R R and R The value of the pulsatory direct current depends upon the resistance of the photo-resistance elements. The resistance of each element depends upon whether it is illuminated or not. In a given case, with photo-resistance elements each having a resistance less than 20 k ohms in the illuminated condition, and from 10 to 1,000M ohms in the non-illuminated condition, the resistance of the series-combination shown in FIGURE 1 was less than 0.36M ohm. If only one diode was not illuminated, the resistance of the series-combination was from 0.9 to 1.34M ohms, and if two diodes were not illuminated, the resistance was upwards of 1.8M ohms. These values diifer sutficiently to ensure with the aid of the resistors R R and R that both tubes B and B are ignited for each half-wave of the pulsatory current if all of the photo-resistance elements are illuminated. If one resistor only is not illuminated, tube B is not ignited and alarm is made with the aid of relay S whereas if two photo-resistance elements are not illuminated, tube B is also not ignited and the whole arrangement is switched off.

FIGURES 2 and 3 show a block 1 of synthetic resin or the like in which neon glow-discharge lamps L are arranged in bores. The photo-resistance elements W are accommodated in bores at right angles to the first mentioned bores as close as possible to the point of maximum light radiation of the neon lamps. The photo-resistance elements and the neon lamps are provided with the shielding caps in order to avoid the influence of daylight. A hood 2 is arranged to enclose the viewing surface 3 so that the neon lamps are clearly visible and the daylight is shielded sutficiently to prevent the photoresistance elements from being influenced thereby.

What is claimed is:

1. Apparatus for supplying a unidirectional current to a load circuit from a source of alternating current, comprising a plurality of semi-conductor rectifier elements connected to said current source and to said load circuit, a plurality of circuits each of which comprises the series combination of a light source and an impedance element, means for connecting said circuits in parallel with individual ones of said rectifier elements, an inverse voltage being developed across each of said rectifier elements by said current source sutficient to ignite its associated light source, a plurality of photosensitive elements connected in series and optically coupled to individual ones of said light sources, a plurality of other impedance elements individually connected in parallel with individual ones of said photosensitive elements, input means for supplying an operating voltage to said photo-sensitive elements, and output circuit means coupled to said photo-sensitive elements for deriving first and second control signals for actuating a control device upon a variation in the inverse voltage across any of said rectifier elements beyond a predetermined value, said control device comprising first and second signal responsive elements coupled to said output circuit means so as to be selectively actuated by said first and second control signals, respectively, said first control signal being operable to actuate said first signal responsive element upon a given variation of the inverse voltage across a first given number of said rectifier elements and said second control signal being operable to actuate said second signal responsive element upon a given variation of the inverse voltage across a second given number of said rectifier elements.

2. Apparatus as described in claim 1 wherein said light sources comprise glow-discharge lamps, said apparatus fur ther comprising a housing for said glow discharge lamps and said photosensitive elements comprising a block of opaque material containing a first group of bores therein and a second group of bores located substantially perpendicular to said first group, means for mounting a glow discharge lamp in each of the bores of said first group and means for mounting a photosensitive element in each of the bores of said second group, each of said bores of said first group being located in juxtaposed relation to a given bore of said second group for optically coupling individual ones of said glow lamps and said photosensitive elements, the bores of said first group containing said glow lamps extending to the outer surface of said block so as to be externally visible.

3. Apparatus as described in claim 2 further comprising a light shield mounted on said block so as to prevent ambient light from entering said first group of bores and thereby to influence the photosensitive elements located in said second group of bores.

4. Apparatus for supplying a unidirectional current to a load circuit from a source of alternating current, comprising a plurality of series connected semiconductor rectifier elements connected in series between said current source and said load circuit, a plurality of gas discharge lamps connected in parallel with individual ones of said rectifier elements, current limiting means connected in series with each of said lamps, an inverse voltage being developed across each of said rectifier elements sufiicient to ignite its associated gas discharge lamp, circuit means comprising a plurality of photosensitive elements connected in series and optically coupled to individual ones of said lamps, said circuit means further comprising in put means for supplying an operating potential thereto and output circuit means for deriving first and second control signals for actuating a control device upon a reduction in the inverse voltage across any of said rectifier elements below a predetermined value, said control device comprising first and second trigger circuits responsive to said first and second control signals, respectively, said first trigger circuit being actuated upon the reduction in the inverse voltage across any one of said rectifier ele ments below said predetermined value and said second trigger circuit being actuated whenever the inverse voltage across two of said rectifier elements fall below said predetermined value.

5. Apparatus as diversified in claim 4 further comprising a plurality of impedance elements individually connected in parallel with individual ones of said photosensitive elements.

6. Apparatus for supplying a unidirectional current to a load circuit from a source of alternating current, comprising a first circuit comprising a plurality of series connected semi-conductor rectifier elements, a second circuit connected in parallel with said first circuit and comprising a plurality of other series connected semiconductor rectifier elements, means for connecting said first and second parallel-connected circuits in series between said current source and said load circuit, a plurality of other circuits each of which comprises the series combination of a gas discharge lamp and an impedance element, means for connecting said other circuits in parallel with individual ones of said rectifier elements, an inverse voltage being developed across each of said rectifier elements by said current source sufiicient to ignite its associated lamp, a plurality of photosensitive elements connected in series and optically coupled to individual ones of said gas lamps, a plurality of other impedance elements individually connected in parallel with individual ones of said photosensitive elements, input means for supplying an operating potential to said photosensitive elements, and output circuit means coupled to said photosensitive elements for deriving a control signal for actuating a control device, said control device comprising first and second signal responsive elements coupled to said output circuit means so as to be selectively actuated by said control signal, said control signal being operable to actuate said first signal responsive element upon a first given variation in the inverse voltage across said rectifier elements and being operable to actuate said second signal responsive element upon a second given variation in the inverse voltage across said rectifier elements.

7. Apparatus as described in claim 6 wherein said current source comprises a polyphase source of alternating current, said apparatus further comprising a plurality of said first and second parallel connected rectifier circuits: equal in number to the number of phases of said poly-- phase source, and means for connecting each phase of said source in series with an individual one of said. parallel connected rectifier circuits and said load circuit.v

8. A monitor system for a plurality of series connected rectifier elements connected in series with a source of alternating current and a load circuit, comprising monitoring means for each of said rectifier elements, each of said monitoring means comprising a light source and an impedance element connected in series with one another and across its respective rectifier element, an in verse voltage being developed across each of said rectifier elements of a value sufiicient to ignite its associated light source, a plurality of photosensitive elements connected in series and optically coupled to individual ones of said light sources, input means for supplying an op erating voltage to said photosensitive elements, and output circuit means coupled to said photosensitive elements for deriving a control signal for actuating a control device, said control device comprising first and second signal responsive elements coupled to said output circuit means so as to be selectively actuated by said control signal, said first signal responsive means being actuated by a first given variation in the inverse voltage across said rectifier elements beyond a predetermined value and a second given variation in the inverse voltage across said rectifier elements beyond a predetermined value.

References Cited by the Examiner UNITED STATES PATENTS 1,922,188 8/1933 Zworykin 317-127 1,940,882 12/1933 Rich 317l27 2,398,366 4/1946 Emley 340253 2,941,187 6/1960 Simjian 250-208 XR 2,982,904 5/1961 Koppelmann 3211l 3,040,178 6/1962 Lyman et al 250-213 3,135,950 6/1964 Finkle 340--237 3,172,093 3/1965 Diebold 340-253 said second signal responsive means being actuated by 15 NEIL C. READ, Primary Examiner. 

1. APPARATUS FOR SUPPLYING A UNIDIRECTIONAL CURRENT TO A LOAD CIRCUIT FROM A SOURCE OF ALTERNATING CURRENT, COMPRISING A PLURALITY OF SEMI-CONDUCTOR RECTIFIER ELEMENTS CONNECTED TO SAID CURRENT SOURCE AND TO SAID LOAD CIRCUIT, A PLURALITY OF CIRCUITS EACH OF WHICH COMPRISES THE SERIES COMBINATION OF A LIGHT SOURCE AND AN IMPEDANCE ELEMENT, MEANS FOR CONNECTING SAID CIRCUITS IN PARALLEL WITH INDIVIDUAL ONES OF SAID RECTIFIER ELEMENTS, AN INVERSE VOLTAGE BEING DEVELOPED ACROSS EACH OF SAID RECTIFIER ELEMENTS BY SAID CURRENT SOURCE SUFFICIENT TO IGNITE ITS ASSOCIATED LIGHT SOURCE, A PLURALITY OF PHOTOSENSITIVE ELEMENTS CONNECTED IN SERIES AND OPTICALLY COUPLED TO INDIVIDUAL ONES OF SAID LIGHT SOURCES, A PLURALITY OF OTHER IMPEDANCE ELEMENTS INDIVIDUALLY CONNECTED IN PARALLEL WITH INDIVIDUAL ONES OF SAID PHOTOSENSITIVE ELEMENTS, INPUT MEANS FOR SUPPLYING AN OPERATING VOLTAGE TO SAID PHOTO-SENSITIVE ELEMENTS, AND OUTPUT CIRCUIT MEANS COUPLED TO SAID PHOTO-SENSITIVE ELEMENTS FOR DERIVING FIRST AND SECOND CONTROL SIGNALS FOR ACTUATING A CONTROL DEVICE UPON A VARIATION IN THE INVERSE VOLTAGE ACROSS ANY OF SAID RECTIFIER ELEMENTS BEYOND A PREDETERMINED VALUE, SAID CONTROL DEVICE COMPRISING FIRST AND SECOND SIGNAL RESPONSIVE ELEMENTS COUPLED TO SAID OUTPUT CIRCUITS MEANS SO AS TO BE SELECTIVELY ACTUATED BY SAID FIRST AND SECOND CONTROL SIGNALS, RESPECTIVELY, SAID FIRST CONTROL SIGNAL BEING OPERABLE TO ACTUATE SAID FIRST SIGNAL RESPONSIVE ELEMENT UPON A GIVEN VARIATION OF THE INVERSE VOLTAGES ACROSS A FIRST GIVEN NUMBER OF SAID RECTIFIER ELEMENTS AND SAID SECOND CONTROL SIGNAL BEING OPERABLE TO ACTUATE SAID SECOND SIGNAL RESPONSIVE ELEMENT UPON A GIVEN VARIATION OF THE INVERSE VOLTAGE ACROSS A SECOND GIVEN NUMBER OF SAID RECTIFIER ELEMENTS. 